This invention relates to a method of laying cables and to various apparatus designed for use with the method, specifically a modified reel for supporting the cable supplied, an unwind guide and a rewind device for rewinding cable drawn from the supply.
The underground laying of cable is a well known technique and has been used for many years to lay electrical and other cables. Often this can be accomplished by simply drawing a plow type device through the ground at the required depth and feeding the cable from a lower end of the plow type device into the ground so that as the plow is drawn along the ground the cable is left under the ground at the required depth. This generally avoids the necessity for digging a trench and a subsequent refilling of the trench.
Such a technique is very effective particularly in areas where there are very few restrictions so that the cable can be layed effectively continuously without halting the technique for roads or railway tracks or other similar obstructions.
Fiber-optics cables have become technically important in recent years and programs are currently under way to lay large lengths of these cables in view of the improved technical performance they provide relative to standard copper cables. However, a serious problem in relation to such cables is the difficulty and expense of splicing cables and hence it is essential to lay the cable in as long a length as possible regardless of any obstructions. The above technique, therefore, is seriously disadvantaged in that it is necessary to halt laying at each obstruction and to provide a technique for overcoming the obstruction and continuing laying on the other side of the obstruction.
Generally this has been carried out by stopping the laying vehicle at the obstruction and unrolling all of the remaining cable on the supply reel into a long loop pulled back in the direction of the previously layed material. When the reel is emptied and the end of the cable found, this is then passed through a bored hole under the obstruction and the laying vehicle transfers to the other side of the obstruction and continues laying while pulling the cable back from the long loop layed out over the ground. This technique is seriously disadvantageous in that the cable is exposed to potential damage by being layed out in an unprotected fashion, secondly it is time consuming and difficult to draw out the cable into the necessary long loop and thirdly the tensions in the cable vary considerably during the pulling out of the loop and also the laying in the ground. This is particularly serious in relation to fiber-optics cables which have a limited resistance to longitudinal tension.